I. Field of the Invention
The present invention is directed to an improvement in vehicle-mounted police radar warning receivers, and more particularly to such a receiver which is powered by a self-contained battery.
II. Description of the Prior Art
Police radar operates at extremely high frequencies such as in the X-band and K-band of the frequency spectrum as discussed in U.S. Pat. No. 4,313,216, assigned to Cincinnati Microwave, Inc., the assignee herein. There are, generally, two types of police radar. One emits a continuous radar signal so long as the radar unit is turned on. The other emits a brief burst of radar signal when the police officer triggers the unit. This latter type is referred to as pulsed or instant-on radar. While transmitting, both continuous and pulsed radar transmit a signal which is at a fixed frequency within the selected band.
An electronic assembly referred to as a police radar warning receiver has been devised to detect the presence of police radar signals. An example is the PASSPORT radar warning receiver manufactured by the assignee herein, Cincinnati Microwave, Inc. of Cincinnati, Ohio. The police radar warning receiver is contained in a box-like housing which may be set on the dash or clipped to the visor of a vehicle, such as a passenger car or truck, motorcycle, boat or the like, which travels on land or water in areas subject to speed-monitoring radar surveillance by police. The front panel of the receiver faces the driver and has various indicators and control knobs.
The operating electronic circuitry employed in the PASSPORT radar warning receiver to determine whether police radar signals are present is described in aforementioned U.S. Pat. No. 4,313,216 and U.S. Pat. Nos. 4,581,769 and 4,750,215, which are also assigned to the assignee hereof. As will be appreciated, the operating circuitry includes an RF front end which actually sweeps through the extremely high frequency police radar band(s) to receive and heterodyne the police radar signal to produce low frequency signals which may then be readily processed to determine whether a police radar signal wa present in the sweep and, if so, to provide audible and/or visual alarms to alert the driver to the presence of police radar.
Typical of many police radar warning receivers is that the operating circuitry is powered from the electrical system of the vehicle with which the receiver is used. To this end, extending from the rear of the housing may be a disconnectable power cord terminating in a plug which is appropriately configured to be received in the vehicle's cigarette lighter socket. The plug transmits electrical energy from the vehicle's electrical system through the cigarette lighter socket to the receiver via the power cord. However, power cords may be a nuisance to the operator of the vehicle.
Many drivers may take the radar warning receiver with them when they leave the vehicle so as to deter theft. If the operator removes the power plug with the receiver, but fails to return the cigarette lighter to the socket, or if the operator leaves the power cord behind, would-be thieves may be alerted to the possibility that a police radar warning receiver is used in that vehicle. The thief might then break into the vehicle on the mistaken belief that the receiver is still somewhere in the vehicle. Further, upon returning to the vehicle, the user must then properly reconnect the power cord or the receiver will not operate. Finally, when it is desired to carry the police radar warning receiver about, such as transferring it from vehicle to vehicle or taking it along after departing the vehicle, transportability of the receiver is hampered due to the extra bulk presented by the power cord.
In an effort to overcome some of the drawbacks associated with powering the receiver circuitry from the vehicle's electrical system, some police radar warning receivers have been offered which contain their own power supply, such as a battery contained within the receiver housing. But the operating electronic circuitry of the radar warning receiver consumes substantial amounts of energy, resulting in the need to frequently replace the battery. Efforts prior to the present invention directed to extending battery life in such battery-powered police radar warning receivers are not believed to have met with much success.